Transient population bypassed by polio vaccination programmes in Yunnan Province, China

Abstract

Four wild strains of polioviruses were isolated between 1995 and April 1996 around the Myanmar border with China. This may have occurred because immunization programs missed certain groups of children who migrated with their parents when they were searching for work. Market tradespeople, in particular, travel with their children. Since it is illegal for persons to live where they are not registered and for parents to have more than the number of children permitted by the family planning law, these children may not participate in national immunization days (NIDs) out of fear of being identified. In September and October of 1996, four markets in Yunnan Province were surveyed to determine the proportion of transients and the prevalence of oral polio vaccine (OPV) immunization; parents and guardians of 127 children, who appeared to be under the age of 5 years, were interviewed. The analysis included 91 children (45 boys and 46 girls), aged 1-3 years, who had complete information. Children were grouped as follows: 1) 37 nontransients who lived where their families were registered; 2) 15 transients from within Yunnan Province; 3) 32 transients from other provinces; and 4) 7 foreign transients. The following information was obtained for each child: 1) whether the child had received a routine OPV; 2) whether the child had a BCG scar; 3) whether the child had ever participated in a NID; and 4) whether the child had participated in the 9 supplementary OPV campaigns since 1990. There were no significant differences in sex or age between groups. As shown in a table of survey results, all indices of immunization were lower in transients. Of the nontransient children, 94.6% had received an OPV; 86.5% had a BCG scar; 89.2% had participated in a NID; and 89.2% had received OPV supplementation. The same figures for all transients as a group were 44.4%, 50.0%, 37.0%, and 38.9%, respectively. For the intraprovincial group, the figures were 66.7%, 46.7%, 60.0%, and 46.7%, respectively. For the extraprovincial group, the figures were 34.4%, 53.1%, 21.9%, and 37.5%, respectively. For foreign transients, the figures were 42.9%, 42.9%, 57.1%, and 28.6%, respectively.